1. Field of the Invention
The present invention relates to a method for transferring semiconductor objects to be processed (hereinafter referred to as “wafers”) between process chambers of a semiconductor processing apparatus.
2. Description of the Related Art
Along with process miniaturization and precision, demand for improvement of the process efficiency for wafers to be processed is also increasing in semiconductor processing apparatuses. In particular, such apparatuses process targets to be processed therein, in which the pressure is reduced. Thus, in recent years, multi-chamber apparatuses have been developed. In the multi-chamber apparatuses, plural process chambers are connected with each other in a single apparatus. The productivity per installation space of the clean room has efficiently been improved. In the apparatuses that include plural process chambers for performing processing, the internal gas or the pressure in each process chamber can adjustably be reduced, and each process chamber is connected to a transport chamber(s) having a robot for transferring wafers.
As the multi-chamber apparatuses, apparatuses having a cluster tool configuration are spreading widely. In the configuration, process chambers are connected radially around the transport chamber. A problem of the cluster tool apparatuses is that they require a large installation space. Particularly, as the recent wafers have a large diameter, the apparatuses require a large installation space. To solve this problem, a new apparatus has a configuration called a linear tool (see Japanese Unexamined Patent Application Publication No. 2007-511104). As the feature of the linear tool, there are plural transport chambers to each of which a process chamber is connected. Further, the transport chambers are connected with each other directly or through a space (hereinafter referred to as an “buffer room”) for receiving and passing the object in between.
Accordingly, the configuration of the linear tool has been proposed for lowering the installation space. On the contrary, some techniques have still been proposed for improving the productivity. For productivity improvement, some important factors are a reduction in the processing period and transferring efficiencies. Particularly, several proposals have been made as a transferring method with high efficiency. A typical transferring method uses a scheduling technique. According to the method with the scheduling, transferring operations are performed based on transferring operations which have been set in advance. In one example of determining the transferring operations, according to a proposed method, process chambers will be assigned as destinations in the order starting from the process completion time (see Japanese Patent Application Laid-Open Publication No. 10-189687).